=head1 NAME
PPIx::Regexp::Element - Base of the PPIx::Regexp hierarchy.
=head1 SYNOPSIS
No user-serviceable parts inside.
=head1 INHERITANCE
C<PPIx::Regexp::Element> is not descended from any other class.
C<PPIx::Regexp::Element> is the parent of
L<PPIx::Regexp::Node|PPIx::Regexp::Node> and
L<PPIx::Regexp::Token|PPIx::Regexp::Token>.
=head1 DESCRIPTION
This class is the base of the L<PPIx::Regexp|PPIx::Regexp>
object hierarchy. It provides the same kind of navigational
functionality that is provided by L<PPI::Element|PPI::Element>.
=head1 METHODS
This class provides the following public methods. Methods not documented
here are private, and unsupported in the sense that the author reserves
the right to change or remove them without notice.
=cut
package PPIx::Regexp::Element;
use strict;
use warnings;
use 5.006;
use Carp;
use List::Util qw{ max min };
use List::MoreUtils qw{ firstidx };
use PPIx::Regexp::Util qw{ __instance };
use Scalar::Util qw{ refaddr weaken };
use PPIx::Regexp::Constant qw{
FALSE
LITERAL_LEFT_CURLY_REMOVED_PHASE_1
MINIMUM_PERL
TOKEN_UNKNOWN
TRUE
};
our $VERSION = '0.056';
=head2 accepts_perl
$token->accepts_perl( '5.020' )
and say 'This works under Perl 5.20';
This method returns a true value if the token is acceptable under the
specified version of Perl, and a false value otherwise. Unless the token
(or its contents) have been equivocated on, the result is simply what
you would expect based on testing the results of
L<perl_version_introduced()|/perl_version_introduced> and
L<perl_version_removed()|/perl_version_removed> versus the given Perl
version number.
This method was added in version 0.051_01.
=cut
sub accepts_perl {
my ( $self, $version ) = @_;
foreach my $check ( $self->__perl_requirements() ) {
$version < $check->{introduced}
and next;
defined $check->{removed}
and $version >= $check->{removed}
and next;
return TRUE;
}
return FALSE;
}
# Return the Perl requirements, constructing if necessary. The
# requirements are simply an array of hashes containing keys:
# {introduced} - The Perl version introduced;
# {removed} - The Perl version removed (or undef)
# The requirements are evaluated by iterating through the array,
# returning a true value if the version of Perl being tested falls
# inside any of the half-open (on the right) intervals.
sub __perl_requirements {
my ( $self ) = @_;
return @{ $self->{perl_requirements} ||=
[ $self->__perl_requirements_setup() ] };
}
# Construct the array returned by __perl_requirements().
sub __perl_requirements_setup {
my ( $self ) = @_;
return {
introduced => $self->perl_version_introduced(),
removed => $self->perl_version_removed(),
};
}
=head2 ancestor_of
This method returns true if the object is an ancestor of the argument,
and false otherwise. By the definition of this method, C<$self> is its
own ancestor.
=cut
sub ancestor_of {
my ( $self, $elem ) = @_;
__instance( $elem, __PACKAGE__ ) or return;
my $addr = refaddr( $self );
while ( $addr != refaddr( $elem ) ) {
$elem = $elem->_parent() or return;
}
return 1;
}
=head2 can_be_quantified
$token->can_be_quantified()
and print "This element can be quantified.\n";
This method returns true if the element can be quantified.
=cut
sub can_be_quantified { return 1; }
=head2 class
This method returns the class name of the element. It is the same as
C<ref $self>.
=cut
sub class {
my ( $self ) = @_;
return ref $self;
}
=head2 comment
This method returns true if the element is a comment and false
otherwise.
=cut
sub comment {
return;
}
=head2 content
This method returns the content of the element.
=cut
sub content {
return;
}
=head2 descendant_of
This method returns true if the object is a descendant of the argument,
and false otherwise. By the definition of this method, C<$self> is its
own descendant.
=cut
sub descendant_of {
my ( $self, $node ) = @_;
__instance( $node, __PACKAGE__ ) or return;
return $node->ancestor_of( $self );
}
=head2 explain
This method returns a brief explanation of what the element does. The
return will be either a string or C<undef> in scalar context, but may be
multiple values or an empty array in list context.
This method should be considered experimental. What it returns may
change without notice as my understanding of what all the pieces/parts
of a Perl regular expression evolves. The worst case is that it will
prove entirely infeasible to implement satisfactorily, in which case it
will be put through a deprecation cycle and retracted.
=cut
sub explain {
my ( $self ) = @_;
my $explanation = $self->__explanation();
my $content = $self->content();
if ( my $main = $self->main_structure() ) {
my $delim = $main->delimiters();
$delim = qr{ \\ (?= [\Q$delim\E] ) }smx;
$content =~ s/$delim//smxg;
}
if ( defined( my $splain = $explanation->{$content} ) ) {
return $splain;
}
return $self->__no_explanation();
}
# Return explanation hash
sub __explanation {
$PPIx::Regexp::NO_EXPLANATION_FATAL
and confess 'Neither explain() nor __explanation() overridden';
return {};
}
# Called if no explanation available
sub __no_explanation {
## my ( $self ) = @_; # Invocant unused
my $msg = sprintf q<No explanation>;
$PPIx::Regexp::NO_EXPLANATION_FATAL
and confess $msg;
return $msg;
}
=head2 error
say $token->error();
If an element is one of the classes that represents a parse error, this
method B<may> return a brief message saying why. Otherwise it will
return C<undef>.
=cut
sub error {
my ( $self ) = @_;
return $self->{error};
}
=head2 in_regex_set
This method returns a true value if the invocant is contained in an
extended bracketed character class (also known as a regex set), and a
false value otherwise. This method returns true if the invocant is a
L<PPIx::Regexp::Structure::RegexSet|PPIx::Regexp::Structure::RegexSet>.
=cut
sub in_regex_set {
my ( $self ) = @_;
my $ele = $self;
while ( 1 ) {
$ele->isa( 'PPIx::Regexp::Structure::RegexSet' )
and return 1;
$ele = $ele->parent()
or last;
}
return 0;
}
=head2 is_quantifier
$token->is_quantifier()
and print "This element is a quantifier.\n";
This method returns true if the element is a quantifier. You can not
tell this from the element's class, because a right curly bracket may
represent a quantifier for the purposes of figuring out whether a
greediness token is possible.
=cut
sub is_quantifier { return; }
=head2 main_structure
This method returns the
L<PPIx::Regexp::Structure::Main|PPIx::Regexp::Structure::Main> that
contains the element. In practice this will be a
L<PPIx::Regexp::Structure::Regexp|PPIx::Regexp::Structure::Regexp> or a
L<PPIx::Regexp::Structure::Replacement|PPIx::Regexp::Structure::Replacement>,
If the element is not contained in any such structure, C<undef> is
returned. This will happen if the element is a
L<PPIx::Regexp|PPIx::Regexp> or one of its immediate children.
=cut
sub main_structure {
my ( $self ) = @_;
while ( $self = $self->parent()
and not $self->isa( 'PPIx::Regexp::Structure::Main' ) ) {
}
return $self;
}
=head2 modifier_asserted
$token->modifier_asserted( 'i' )
and print "Matched without regard to case.\n";
This method returns true if the given modifier is in effect for the
element, and false otherwise.
What it does is to walk backwards from the element until it finds a
modifier object that specifies the modifier, whether asserted or
negated. and returns the specified value. If nobody specifies the
modifier, it returns C<undef>.
This method will not work reliably if called on tokenizer output.
=cut
sub modifier_asserted {
my ( $self, $modifier ) = @_;
defined $modifier
or croak 'Modifier must be defined';
my $elem = $self;
while ( $elem ) {
if ( $elem->can( '__ducktype_modifier_asserted' ) ) {
my $val;
defined( $val = $elem->__ducktype_modifier_asserted( $modifier ) )
and return $val;
}
if ( my $prev = $elem->sprevious_sibling() ) {
$elem = $prev;
} else {
$elem = $elem->parent();
}
}
return;
}
=head2 next_element
This method returns the next element, or nothing if there is none.
Unlike L<next_sibling()|/next_sibling>, this will cross from the content
of a structure into the elements that define the structure, or vice
versa.
=cut
sub next_element {
my ( $self ) = @_;
my $parent = $self->_parent()
or return;
my $inx = $self->__my_inx();
return ( $parent->elements() )[ $inx + 1 ];
}
=head2 next_sibling
This method returns the element's next sibling, or nothing if there is
none.
=cut
sub next_sibling {
my ( $self ) = @_;
my ( $method, $inx ) = $self->__my_nav()
or return;
return $self->_parent()->$method( $inx + 1 );
}
=head2 parent
This method returns the parent of the element, or undef if there is
none.
=cut
sub parent {
my ( $self ) = @_;
return $self->_parent();
}
=head2 perl_version_introduced
This method returns the version of Perl in which the element was
introduced. This will be at least 5.000. Before 5.006 I am relying on
the F<perldelta>, F<perlre>, and F<perlop> documentation, since I have
been unable to build earlier Perls. Since I have found no documentation
before 5.003, I assume that anything found in 5.003 is also in 5.000.
Since this all depends on my ability to read and understand masses of
documentation, the results of this method should be viewed with caution,
if not downright skepticism.
There are also cases which are ambiguous in various ways. For those see
the L<PPIx::Regexp|PPIx::Regexp> documentation, particularly
L<Changes in Syntax|PPIx::Regexp/Changes in Syntax>.
Very occasionally, a construct will be removed and then added back. If
this happens, this method will return the B<lowest> version in which the
construct appeared. For the known instances of this, see
the L<PPIx::Regexp|PPIx::Regexp> documentation, particularly
L<Equivocation|PPIx::Regexp/Equivocation>.
=cut
sub perl_version_introduced {
return MINIMUM_PERL;
}
=head2 perl_version_removed
This method returns the version of Perl in which the element was
removed. If the element is still valid the return is C<undef>.
All the I<caveats> to
L<perl_version_introduced()|/perl_version_introduced> apply here also,
though perhaps less severely since although many features have been
introduced since 5.0, few have been removed.
Very occasionally, a construct will be removed and then added back. If
this happens, this method will return the C<undef> if the construct is
present in the highest-numbered version of Perl (whether production or
development), or the version after the highest-numbered version in which
it appeared otherwise. For the known instances of this, see the
L<PPIx::Regexp|PPIx::Regexp> documentation, particularly
L<Equivocation|PPIx::Regexp/Equivocation>.
=cut
sub perl_version_removed {
return undef; ## no critic (ProhibitExplicitReturnUndef)
}
=head2 previous_element
This method returns the previous element, or nothing if there is none.
Unlike L<previous_sibling()|/previous_sibling>, this will cross from
the content of a structure into the elements that define the structure,
or vice versa.
=cut
sub previous_element {
my ( $self ) = @_;
my $parent = $self->_parent()
or return;
my $inx = $self->__my_inx()
or return;
return ( $parent->elements() )[ $inx - 1 ];
}
=head2 previous_sibling
This method returns the element's previous sibling, or nothing if there
is none.
This method is analogous to the same-named L<PPI::Element|PPI::Element>
method, in that it will not cross from the content of a structure into
the elements that define the structure.
=cut
sub previous_sibling {
my ( $self ) = @_;
my ( $method, $inx ) = $self->__my_nav()
or return;
$inx or return;
return $self->_parent()->$method( $inx - 1 );
}
=head2 requirements_for_perl
say $token->requirements_for_perl();
This method returns a string representing the Perl requirements for a
given module. This should only be used for informational purposes, as
the format of the string may be subject to change.
At the moment, the returns may be:
version <= $]
version <= $] < version
two or more of the above joined by '||'
! $]
The last means that, although all the components of the regular
expression can be compiled by B<some> version of Perl, there is no
version that will compile all of them.
I reiterate: the returned string may be subject to change, maybe without
warning.
This method was added in version 0.051_01.
=cut
sub requirements_for_perl {
my ( $self ) = @_;
my @req;
foreach my $r ( @{ $self->__structured_requirements_for_perl() || [] } ) {
push @req, defined $r->{removed} ?
"$r->{introduced} <= \$] < $r->{removed}" :
"$r->{introduced} <= \$]";
}
@req
or return '! $]';
return join ' || ', @req;
}
=head2 scontent
This method returns the significant content of the element. That is, if
called on the parse of C<'/ f u b a r /x'>, it returns C<'/fubar/x'>. If
the invocant contains no insignificant elements, it is the same as
L<content()|/content>. If called on an insignificant element, it returns
nothing -- that is, C<undef> in scalar context, and an empty list in
list context.
This method was inspired by jb's question on Perl Monks about stripping
comments and white space from a regular expression:
L<http://www.perlmonks.org/?node_id=1207556>
This method was added in version 0.053_01
=cut
sub scontent {
return;
}
=head2 significant
This method returns true if the element is significant and false
otherwise.
=cut
sub significant {
return 1;
}
=head2 snext_element
This method returns the next significant element, or nothing if
there is none.
Unlike L<snext_sibling()|/snext_sibling>, this will cross from
the content of a structure into the elements that define the structure,
or vice versa.
=cut
sub snext_element {
my ( $self ) = @_;
my $inx = $self->__my_inx();
my $parent = $self->_parent()
or return;
my @elem = $parent->elements();
while ( 1 ) {
$inx++;
$elem[$inx]
or last;
$elem[$inx]->significant()
and return $elem[$inx];
}
return;
}
=head2 snext_sibling
This method returns the element's next significant sibling, or nothing
if there is none.
This method is analogous to the same-named L<PPI::Element|PPI::Element>
method, in that it will not cross from the content of a structure into
the elements that define the structure.
=cut
sub snext_sibling {
my ( $self ) = @_;
my $sib = $self;
while ( defined ( $sib = $sib->next_sibling() ) ) {
$sib->significant() and return $sib;
}
return;
}
=head2 sprevious_element
This method returns the previous significant element, or nothing if
there is none.
Unlike L<sprevious_sibling()|/sprevious_sibling>, this will cross from
the content of a structure into the elements that define the structure,
or vice versa.
=cut
sub sprevious_element {
my ( $self ) = @_;
my $inx = $self->__my_inx()
or return;
my $parent = $self->_parent()
or return;
my @elem = $parent->elements();
while ( $inx ) {
$elem[--$inx]->significant()
and return $elem[$inx];
}
return;
}
=head2 sprevious_sibling
This method returns the element's previous significant sibling, or
nothing if there is none.
This method is analogous to the same-named L<PPI::Element|PPI::Element>
method, in that it will not cross from the content of a structure into
the elements that define the structure.
=cut
sub sprevious_sibling {
my ( $self ) = @_;
my $sib = $self;
while ( defined ( $sib = $sib->previous_sibling() ) ) {
$sib->significant() and return $sib;
}
return;
}
# NOTE: This method is to be used ONLY for requirements_for_perl(). I
# _may_ eventually expose it, but at the moment I do not consider it
# stable. The exposure would be
# sub structured_requirements_for_perl {
# my ( $self ) = @_;
# return $self->__structured_requirements_for_perl();
# }
# The return ia a reference to an array of hashes. Each hash contains
# key {introduced} (the version the element was introduced) and MAYBE
# key {removed} (the version the element was removed). There may be more
# than one such, and their ranges will not overlap.
sub __structured_requirements_for_perl {
my ( $self, $rslt ) = @_;
$rslt ||= $self->__structured_requirements_for_any_perl();
my @merged;
foreach my $left ( $self->__perl_requirements() ) {
foreach my $right ( @{ $rslt } ) {
my $min = max( $left->{introduced}, $right->{introduced} );
my $max = defined $left->{removed} ?
defined $right->{removed} ?
min( $left->{removed}, $right->{removed} ) :
$left->{removed} :
$right->{removed};
defined $max
and $max <= $min
and next;
push @merged, {
introduced => $min,
removed => $max,
};
}
}
@{ $rslt } = @merged;
return $rslt;
}
# NOTE: This method is to be used ONLY to initialize
# __structured_requirements_for_perl(). It returns a structure that
# matches any Perl.
sub __structured_requirements_for_any_perl {
return [
{
introduced => MINIMUM_PERL,
removed => undef,
},
];
}
=head2 tokens
This method returns all tokens contained in the element.
=cut
sub tokens {
my ( $self ) = @_;
return $self;
}
=head2 top
This method returns the top of the hierarchy.
=cut
sub top {
my ( $self ) = @_;
my $kid = $self;
while ( defined ( my $parent = $kid->_parent() ) ) {
$kid = $parent;
}
return $kid;
}
=head2 unescaped_content
This method returns the content of the element, unescaped.
=cut
sub unescaped_content {
return;
}
=head2 whitespace
This method returns true if the element is whitespace and false
otherwise.
=cut
sub whitespace {
return;
}
=head2 nav
This method returns navigation information from the top of the hierarchy
to this node. The return is a list of names of methods and references to
their argument lists. The idea is that given C<$elem> which is somewhere
under C<$top>,
my @nav = $elem->nav();
my $obj = $top;
while ( @nav ) {
my $method = shift @nav;
my $args = shift @nav;
$obj = $obj->$method( @{ $args } ) or die;
}
# At this point, $obj should contain the same object
# as $elem.
=cut
sub nav {
my ( $self ) = @_;
__instance( $self, __PACKAGE__ ) or return;
# We do not use $self->parent() here because PPIx::Regexp overrides
# this to return the (possibly) PPI object that initiated us.
my $parent = $self->_parent() or return;
return ( $parent->nav(), $parent->__nav( $self ) );
}
# Find our index among the parents children. If not found, just return.
# Unlike __my_nav(), this just returns an index, which is appropriate
# for ->element( $inx ), or would be if element() existed.
sub __my_inx {
my ( $self ) = @_;
my $parent = $self->_parent() or return;
my $addr = refaddr( $self );
my $inx = firstidx { refaddr $_ == $addr } $parent->elements();
$inx < 0
and return;
return $inx;
}
# Find our location and index among the parent's children. If not found,
# just returns.
{
my %method_map = (
children => 'child',
);
sub __my_nav {
my ( $self ) = @_;
my $parent = $self->_parent() or return;
my $addr = refaddr( $self );
foreach my $method ( qw{ children start type finish } ) {
$parent->can( $method ) or next;
my $inx = firstidx { refaddr $_ == $addr } $parent->$method();
$inx < 0 and next;
return ( $method_map{$method} || $method, $inx );
}
return;
}
}
{
my %parent;
# no-argument form returns the parent; one-argument sets it.
sub _parent {
my ( $self, @arg ) = @_;
my $addr = refaddr( $self );
if ( @arg ) {
my $parent = shift @arg;
if ( defined $parent ) {
__instance( $parent, __PACKAGE__ ) or return;
weaken(
$parent{$addr} = $parent );
} else {
delete $parent{$addr};
}
}
return $parent{$addr};
}
sub __parent_keys {
return scalar keys %parent;
}
}
# Bless into TOKEN_UNKNOWN, record error message, return 1.
sub __error {
my ( $self, $msg ) = @_;
defined $msg
or $msg = 'Was ' . ref $self;
$self->{error} = $msg;
bless $self, TOKEN_UNKNOWN;
return 1;
}
# This huge kluge is required by
# https://rt.perl.org/Ticket/Display.html?id=128213 which means the
# deprecation will be done in at least two separate phases. It exists
# for the use of PPIx::Regexp::Token::Literal->perl_version_removed, and
# MUST NOT be called by any other code.
# Note that the perldelta for 5.25.1 and 5.26.0 do not acknowledge tha
# phased deprecation, and pretend that everything was done on the phase
# 1 schedule. This appears to be deliberate per
# https://rt.perl.org/Ticket/Display.html?id=131352
sub __following_literal_left_curly_disallowed_in {
return LITERAL_LEFT_CURLY_REMOVED_PHASE_1;
}
# Called by the lexer to record the capture number.
sub __PPIX_LEXER__record_capture_number {
my ( undef, $number ) = @_; # Invocant unused
return $number;
}
# Called by the lexer to rebless
sub __PPIX_ELEM__rebless {
my ( $class, $self ) = @_; # %arg unused
$self ||= {};
bless $self, $class;
delete $self->{error};
defined $self->{error}
and return 1;
delete $self->{error};
return 0;
}
sub DESTROY {
$_[0]->_parent( undef );
return;
}
1;
__END__
=head1 SUPPORT
Support is by the author. Please file bug reports at
L<http://rt.cpan.org>, or in electronic mail to the author.
=head1 AUTHOR
Thomas R. Wyant, III F<wyant at cpan dot org>
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2009-2018 by Thomas R. Wyant, III
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl 5.10.0. For more details, see the full text
of the licenses in the directory LICENSES.
This program is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose.
=cut
# ex: set textwidth=72 :